Three whales – an adult and two calves – could be seen circling the swimmer. The largest orca is filmed nipping Johnson's toes.
In spite of their gruesome nickname, killer whales are quite playful. As with dolphins, it is not unusual for pods of the large marine mammals join ocean swimmers.
Johnson said afterwards the experience was "better than winning the lotto" but the odds of seeing whales around New Zealand are more favourable than that.
Kaikoura is a favourite with whale watchers. Photo / Getty Images
Here's our guide to whale watching to increase your chances of a sighting around the Kiwi coastline:
The Kaikōura coastal drive has long been a favourite of whale watchers. In winter, between June to August, migrating sperm whales follow the coast north. Whale Watch runs cruises for budding marine naturalists four times a day, though it's not uncommon to be able to see the giant tails of sperm whales from the shore.
Gannets stay at bay while this Orca swims past the coast near Auckland. Photo / Getty Images
Hauraki Gulf
Just outside of Auckland, orca and bottlenose dolphins have been known to swim right into the harbour. Bryde's whales are often seen in the Hauraki Gulf but do not enter the harbour. Auckland Whale and Dolphin Safari runs regular trips for tourists out into the waters east of Auckland
A Killer whale plays in the surf of a Northland beach. Photo / Mike Cunningham, Getty Images
Bay of Islands
The northern bay offers almost daily sightings for resident bottle nose dolphins. However migratory whales such as pilot whales and humpbacks pass though the islands north to south between August and September and on the return leg March to April. Blue whales have even been sighted here.
A pod of Orca swim off New Zealand's east coast. Photo / Getty Images
Coromandel
The waters of Mercury Bay and the popular Christmas beaches of Hahei, Cathedral Cove are known to be migration routes for marine mammals. The warmer waters of the Kiwi summer are known to draw whales past on the way to Tonga or Australia, but whales can be seen right through the six month window of October – March.
Dolphins chase a pleasure craft through Marlborough Sound. Photo / Getty Images
Marlborough Sounds
In the middle of the migratory route, Marlborough is a prime whale watching spot. Unsurprisingly it was a hub for New Zealand's whaling fleet, though now boats aim to capture the marine mammals with cameras rather than harpoons. Between June and July, the Cook Straight is the best place to see migrating baleen whales.
DoC's advice to would-be whale watchers
The stunning drone footage of this encounter is extremely timely. This summer, the Department of Conservation is running a campaign to educate tourists and amateur drone photographers on how to best appreciate and respect animals they encounter in the wild.
Illustration / NZ Herald
"Give wildlife their space," is the DoC's key message to wildlife watchers.
"While you might want to get close to our seals, birds, dolphins and other wildlife, keeping your distance is important to avoid stress and harm to wildlife."
After the recent strandings on Stewart Island, the DoC urges anyone to call their hotline 0800 DOC HOT (0800 362 468) immediately if they sight a distressed marine mammal.
Drone pilots should come no closer than 150m to the whale or dolphin and avoid flying directly over the animals.
The DoC also warns whale watchers that anyone charged with "harassing, disturbing, injuring or killing a marine mammal faces a maximum penalty of two years imprisonment or a fine to maximum of $250,000."
